Copper base alloy



United States Patent 3,258,334 COPPER BASE ALLOY Edward V. Kessler, North Hills, Pa., assignor t0 International Copper Research Association, Inc. No Drawing. Filed Jan. 8, 1964, Ser. No. 336,385 7 Claims. (Cl. 75-159) This invention relates to a copper base alloy and more particularly it relates to a nickel-aluminum bronze containing cobalt as an alloying element and substantially free of lead, tin and other impurities. The alloy of the present invention has properties which are suitable in the manufacturing of molds for the production of blown or press molded glass and plastic articles.

In the glass industry cast iron has been used extensively as a basic mold material for the production of molded glassware. Its low tensile and yield strengths combined with low resistance to oxidation and thermal cracking have created difiiculties in production where the demands on the molds are severe. Several alloys having higher tensile and yield strengths and other desirable properties, notably the nickel-aluminum bronze containing beryllium or vanadium, have been developed as possible replacements for the cast iron. However, up to the present time their use in the glass industry is limited. The failure of these alloys to gain wider industrial acceptance is due partly to their high costs because of the expensive alloying additives and partly to the properties of the alloys which fail to satisfy all requirements as a basic mold material.

This invention provides a low cost copper base alloy having properties that are suitable for broad glass industry use and particularly in the manufacturing of molds for the production of glass articles. The copper base alloy of this invention, which is substantially free of lead, tin and other impurities, has a composition comprising 13.5 to 16.5 percent of nickel, 9.0 to 11.0 percent of aluminum, 1.0 to 2.0 percent of cobalt and the balance copper. A small amount of iron, generally in the range of 0.4 to 1.0 percent, is also present in the alloy. The percentages of elements in the alloy are percent by weight. The allowable amount of impurities in the alloy is small. A typical alloy of this invention comprises the following elements within the range indicated below:

Elements: Percent by weight Ni 13.5-16.5 A1 9.011.0 Co 1.0-2.0 Fe 0.4-1.0 Pb 0.005 max. Sn 0.02 max. Sb Nil Si Nil Others (As, Bi, P, S, Zn) 0.25 max. Cu Balance The tensile and the yield strengths of this alloy at room temperature are above 90,000 p.s.i. and 55,000 p.s.i. respectively. At elevated temperatures the strengths of the alloy are lower, but still remain at high levels. For example, at 800 F. the tensile and the yield strengths of the alloy are above 53,000 and 40,000 p.s.i. respectively, and at 1,000 F. they are above 38,000 and 28,000 p.s.i. respectively. The high tensile and yield strengths of this alloy are significant for the production of glass molds, particularly in view of the fact that the normal tensile strength of a glass mold made of cast iron is only approximately 25,000 p.s.i. at room temperature and this strength decreases steadily as the operating temperature increases.

Higher tensile and yield strengths of this alloy enable it to provide higher attendant surface hardness and also improve abrasion resistance at elevated temperatures. Table 1 shows the physical properties of two typical alloys of this invention, designated as Alloy I and Alloy II. Alloy I comprises 73.0 percent copper, 9.50 percent aluminum, 0.50 percent iron, 2.00 percent cobalt and 15.0 percent nickel, and Alloy II comprises 74.0 percent copper, 9.50 percent aluminum, 0.50 percent iron, 1.00 percent cobalt and 15.0 percent nickel.

TAB LE 1.-PHYSICAL P ROPE RTIE S Tensile, Yield, Elonga- Reduction Alloy Temperature p.s.i. p.s.i. tion, of area, percent percent As previously stated, it is important that the alloy of this invention be substantially free of impurities, especially lead and tin. I have found a lead content much above 0.005% and a tin content of much above 0.02% will adversely affect the hot strength of the alloy. Similarly, a zinc impurity in the alloy causes mold pitting in service at elevated temperatures and poor weldability during repairing and refinishing operations. To illustrate the effect of lead and tin on the hot strength of this alloy, an initial alloy having a nominal composition of 15.0 percent nickel, 10.0 percent aluminum, 0.75 percent iron, 1.50 percent cobalt and the balance copper, which is designated as Alloy III, was used for the test. Six sample specimens were made using this initial alloy. With the exception of Sample 1, various small amounts of lead and tin were added in the subsequent samples and their tensile and yield strengths at room temperature, 800 F. and 1000 F. are recorded in Tables 2, 3 and 4. The data from these tables clearly show that the tensile and yield strengths of the alloy at elevated temperatures are greatly affected by the addition of lead and tin.

TABLE 2.ROOM TEMPERATURE Yield, Tensile, Elonga- Sample Additions p.s.i. in p.s.i. in tion,

Lbs. Lbs. percent 1 Normal 60, 600 91, 000 9. 5 .02% Pb added. 59, 800 88, 500 2. 5 05% Pb addetL... 60, 000 88, 000 3. 5 10% Pb added 55, 000 87, 000 3 027% Sn added 65, 000 107, 000 5 .44% Sn added 56, 000 87, 000 2 TABLE 3.800 F. TEMPERATURE Yield, Tensile, Elonga- Sample Additions p.s.i. in p.s.i. in tio Lbs. Lbs. percent 1 Normal 46, 000 54, 000 3. 5

.02% Pb added 14, 000 24, 000 0. 25 05% Pb added 13, 500 19, 000 1 .l0% Pb added 11, 500 17,500 0. 25 027% Sn added 20, 000 45, 500 0. 25 .44% Sn addetL... 30,000 45, 000 1 properties of this alloy for the manufacturing of glass molds are described below as specific examples. In all of these examples, Alloy III, having a nominal composition of 15.0% nickel, 10.0% aluminum, 0.75% iron, 1.50% cobalt and the balance copper, was used.

Example 1 Repeated thermal shock from rapid heating and cooling causes one mode of failure commonly encountered in glass molds. The property of the alloy to withstand the thermal shock was tested using an annular disc 3" in diameter and thick. Eight holes having A diameter were drilled through the disc at symmetrical positions to check the crack of the specimen under test conditions. Four additional holes A" in diameter and /s" thick were provided on the surface of the disc for temperature control. Thermocouples were attached to the disc to determine the temperature changes. In the test an oxyacetylene flame was directed on the disc surface heating the disc to 1000 F. Immediately after heating, a force air blast was used to shock cool the disc to 300 F. Both the heating and the cooling times were 1% minutes. This shock treatment was repeated for 1,700 cycles and no sign of cracking on the disc was observed. A similar disc made of cast iron used in conventional glass molds was tested in identical fashion. The required heating and cooling times were 3 minutes and 2 /2 minutes respectively. The cast iron disc failed after only 338 cycles.

Example 2 The oxidation resistance of the alloy of this invention was tested using a /2" cube. The specimen was placed in a furnace exposed in air at 1600" F. After 4 hours at that temperature, the specimen was removed and air cooled to room temperature. This cycle was repeated on sets for 2, 4, 8, 16 and 32 times. The change in dimensions of the cube were measured and are tabulated in Table 5.

TABLE 5.OXIDATION EXPERIMENT [Each cycle 1600 for 4 hours then cool to room temperature] Example 3 The thermal stability in terms of thermal growth of this alloy was tested using a cylindrical specimen 1.128" in diameter and 1" thick. The specimen was heated to 1000 F. and maintained at this temperature for 168 hours before it was allowed to cool to room temperature. The dimension change was noted by measuring the height of the cylinder at 4 different and equally spaced points (A, B, C and D) before and after the heating. This sequence was repeated for 10 cycles for a total of 1680 hours. The result of this test is tabulated in Table 6. For comparison, cast iron mold material was identically tested and the result is tabulated in Table 7. Again the unusual thermal stability of this alloy as compared to that of the cast iron is apparent from the tables.

TABLE 6.ELEVATED TEMPERATURE GROWTH AND WEIGHT GAIN OF ALLOY III Time (Hours) A B C D Weight,

Grams TABLE 7.-ELEVATED TEMPERATURE GROWTH AND WEIGHT GAIN OF CAST IRON MOLD Time (Hours) A B O D Weight,

Grams Example 4 Heat transfer is an extremely important parameter in determining the performance of a glass mold material. The nature of heat flow in a particular mold is obviously dependent on the thermal characteristics of the metal as well as the design of the mold cooling surfaces and its Cast Iron Alloy III Before After Difference Before After Dlfierence 2 Cycles Sample #2:

Vertical 562 573 011 561 564 003 Horizontal 5635 572 009 561 564 003 4 Cycles Sample #4:

Vertical -1 561 595 034 561 553 002 Horizontal 561 597 036 561 563 002 8 Cycles Sample #6:

Ver cal 561 619 058 562 564 002 Horizontal 562 622 060 561 564 004 16 Cycles Sample #8:

Vertical 561 650 089 560 563 003 Horizontal 560 650 090 562 566 004 32 Cycles Sample #10:

Vertical 561 703 142 515 517 002 Horizontal 561 696 134 5185 5205 002 The change in dimension is a measure of both oxide formation and growth as Well as any phase change or stress relief eifect occurring under cyclic temperature conditions. The unusual resistance of this alloy is immediately apparent as compared to a cast iron mold material tested under identical conditions and tabulated in the same table.

mode of forced cooling. The thermal conductivity of this alloy was measured from room temperature to 1600 F. using the absolute radial heat flow technique of R. W. Powell. In this method a vertical stack of flat annular rings is heated by an electric heater centered in the axial hole. The annular heat flow is measured by thermocouples placed on the inner and outer surfaces of the cylinder.

Heat input is calculated from the power input to the center portion of the axial heater.

In the test the power input was controlled to yield in hardness is expected at increasing mold temperature. Cast iron has a very similar hardness vs. temperature characteristic.

TABLE 8.-HOT HARDNESS OF ALLOY III [Brinell hardness numbers, hr. at temperature] Sample 1 Sample 2 Sample 3 Test Temp., F.

Test Temp., F. Test Temp, F.

an approximate radial thermal gradient as well as a particular average temperature level. Calculation of the thermal conductivity was based on the power input, the stack geometry and the measured gradient. The result of the test shows that the thermal conductivity of this alloy increase linearly from 27 B.t.u. (hr.)/ (sq. ft.)/ F./'ft.) at 200 F. to 55 B.t.u./(hr.)/(sq. ft.)/( F./ft.) at 1600 F., which is a significant feature of the present alloy. Thermal conductivity of conventional cast iron mold material containing 3.19 percent carbon, 1.57 percent silicon and 0.90 percent manganese decreases linearly as temperature increases. At a mold temperature of 1000 F. the thermal conductivity of the present alloy is 168 percent higher than that of the cast iron.

Example 5 Failure of a given mold by thermal fatigue is very much a function of the mold size, size of the article and the type of glass. Large charges of glass at high temperature are obviously more deleterious. To determine this property of the present alloy, two forms of fatigue tests were employed; one employing .pre-set temperature limits between which cycling took place and the second using pre-selected heat input with constant cooling time for each cycle. Of these two tests, the latter is more representative of the glass making thermal cycle.

The apparatus employed for these tests consists of a restraining frame, a power source to provide resistance heating of the specimen and load cells to record the induced thermal stresses. The specimen for testing is heated by a controlled electrical current and is cooled by heat conduction at the cooled grips, as well as by convection in still air. The restraint of the frame develops a stress whose magnitude depends on the maximum temperature achieved.

In the pre-set temperature limit cycle, the alloy of this invention was tested between 300 'F. and 1000 F. and it failed after 841 cycles.

In the constant heat input cycle, cast iron was first tested over the range 300 F. to 1000 F. and the specimen failed after '63 cycles. Employing this same power input to the alloy of the present invention yielded temperature limits of 125 F. to 500 R, an indication of the higher thermal diffusivity of this alloy. The alloy of the present invention was first cycled 63 times to duplicate the failure point for cast iron, and at this stage it gave no evidence of incipient failure. A second specimen made of the present alloy showed no evidence of failure after 1540 cycles.

Example 6 The ability of a glass mold to resist scoring by oxide particles or accidental scratching in service or in assembly is primarily a function of its room and elevated temperature hardness. Hot hardness tests were carried out using a 5MM carbide ball and a 125 kg. load. The results of this test are presented in Table 8. The decrease applications.

Example 7 The design of close tolerance glassware depends on an accurate knowledge of thermal expansion characteristics of the mold material. Determination of this characteristic of the present alloy was made on as cast material from room temperature to 1500 F. The mean coefficient and the instantaneous coefiicient for thermal expansion of the alloy are constant up to 1000 F. The values of the mean and instantaneous coefficients up to 1000" F. are 9.4 and 9.5 inch/inch/ F. 10 respectively. Deviation from constant at higher temperature is believed to be the result of either a precipitation reaction or a relief of residual stress. For good mold stability at normal operating temperature a stabilizing treatment at a temperature several hundred degrees higher than the maximum service temperature would eliminate this shortcoming.

These specific examples clearly demonstrate that the alloy of this invention exhibits an excellent combination of mechanical and physical properties at both room and elevated temperature as a glass mold material. Particularly impressive is its high thermal conductivity at elevated temperature; a property which would predict higher production rates, as well as longer mold life as a result of lower operating temperature. The combination of thermal and mechanical properties of this alloy make it extremely resistant to thermal fatigue or cracking. Its low oxidation rate at normal mold operating temperatures virtually eliminates glass rejects due to surface flaking and spalling.

In addition to these desirable properties, the process metallurgy of this alloy is equally attractive. It is heat treatable as a result of intermetallic compound precipitation and as a result of phase decomposition. Oxygen and nitrogen present in the alloy as impurities probably also contribute to the aging process through oxide or nitride precipitation. The alloy of this invention is also forgeable and weldable. The forgeability enables the production of pre-machined parts and for the reduction of the as-cast structure. Its weldability enables the mold to be repaired. and still retain the characteristics of the alloy at the weld.

This alloy, while I found it to be particularly attractive as a mold material for the glass industry, also has other Its favorable process metallurgy combined with the excellent mechanical and physical characteristics indeed suggest unlimited application in other industries such as for the production of marine products, and control apparatus.

I claim:

1. A copper base alloy substantially free of lead and tin comprising 13.5 to 16.5 percent by weight of nickel, 9.0 to 11.0 percent of aluminum, 1.0 to 2.0 percent of cobalt and the balance copper, said percentages being percent by weight.

2. A copper base alloy substantially free of lead and tin, and having a composition comprising the following elements and within the range indicated below:

Percent by weight Nickel 13.516.5 Aluminum 9.01l.0

Cobalt 1.0-2.0

Iron 0.4-1.0 Copper "1--..-- Balance 3. A copper base alloy having a composition comprising the following elements and within the range indicated below:

Nickel 13.5-16.5 percent by weight. Aluminum 9.0-1l.0 percent by weight.

Cobalt 1.02.0 percent by weight.

Iron 0.4-1.0 percent by weight.

Lea-d 0.005 percent by weight maximum. Tin 0.02 percent by weight maximum. Others 0.25 percent by Weight maximum. Copper Balance.

4. A copper base alloy, substantially free of lead and tin, comprising the composition as follows:

Percent by weight Nickel 15 Aluminum Iron 0.75

Cobalt 1.50 Copper Balance 5. A copper base alloy having properties which are particularly suitable in the manufacturing of molds for the production of pressed and molded glass and plastic articles, having a nominal composition comprising the following elements and within the range indicated below:

Percent by weight Nickel 13.5-16.5

Aluminum 9.0-1 1.0 Cobalt 1.0-2.0

Iron O.4-1 .0

Copper Balance said alloy being substantially free of impurities and having less than 0.02 percent by weight of tin and 0.005 percent by weight of lead.

6. A copper base alloy having properties which are particularly suitable for the manufacturing of molds for the production of pressed and molded glass and plastic articles, said alloy consisting essentially of the following nominal composition:

Percent by Weight Copper 73.0 Aluminum 9.5

Iron 0.5

Cobalt 2.0

Nickel 15.0

Copper 74.0 Aluminum 9.5

Iron 0.5

Cobalt 1 .0

Nickel 15 .0

said alloy being substantially free of impurities and having less than 0.02 percent by weight of tin and 0.005 percent by weight of lead.

References Cited by the Examiner UNITED STATES PATENTS 1,369,818 3/1921 Kosugi -162 X 1,481,782 1/1924 'Iytaka 75-162 X 3,156,559 11/1964 Klement 75-162 FOREIGN PATENTS 569,344 1/1924 France.

DAVID L. RECK, Primary Examiner.

C. N. LOVELL, Assistant Examiner. 

2. A COPPER BASE ALLOY SUBSTANTIALLY FREE OF LEAD AND TIN, AND HAVING A COMPOSITION COMPRISING THE FOLLOWING ELEMENTS AND WITHIN THE RANGE INDICATED BELOW: 